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243: Medical Microbiology > 16. Virology Introduction > Flashcards

16. Virology Introduction Flashcards

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Biology 101 flashcards USMLE® Step 1 flashcards
1
Q

name a small virus

A

parvovirus

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2
Q

name a cylindrical virus

A

tobacco mosaic virus

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3
Q

why are viruses intracellular parasites

A

they have no capacity to perform any metabolism outside a host cell

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4
Q

viruses are obligate, what does this mean?

A

no replication cycle outside the host cell

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5
Q

how many virus particles on earth

A

10^23

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6
Q

why is taxonomy important in viruses

A

allows us to draw evolutionary conclusions on viruses and determine any ancestry

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7
Q

what did taxonomic classification of SARS-CoV2 show?

A

showed it to be a relative of SARS-CoV1

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8
Q

how did Linnaeus classify organisms

A

heirarchically: kingdom, phyla, class, order, family…

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9
Q

what does the Baltimore classify organisms on

what does this allow?

A

genome structure

allows us to group viruses that behave similarly in distinct groups

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10
Q

what are types 1-3 of the Baltimore classification system

A

type 1: dsDNA viruses
type 2: ssDNA viruses
type 3: dsRNA viruses

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11
Q

what are types 4-6 of the Baltimore classification system

A

type 4: positive sense ssRNA viruses
type 5: negative sense ssRNA viruses
type 6: ssRNA viruses (reverse transcriptase -> dsDNA)

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12
Q

what Baltimore class does Ebola belong to

A

class 5

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13
Q

what Baltimore class does SARS-CoV2 belong to

A

class 4

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14
Q

what is the …. of covid 19?

  • species
  • genus
  • family
A

species: severe acute respiratory syndrome- related coranovirus
genus: betacoronavirus
family: coronaviridae

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15
Q

what is the opposite of filamentous

A

icosahedral

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16
Q

what does filamentous mean

A

forms filaments from protein subunits arranged in rings

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17
Q

give an example of a filamentous virus

A

tobacco mosaic virus = RNA genome surrounded by protein subunits

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18
Q

what does icosahedral structure mean?

A

complex crystalline structure that fit together to form a sphere (sort of like a football)

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19
Q

by what two ways can a virus be encapsulated

A

via capsid or lipid bilayer

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20
Q

in a bi-lipid envelope, where is the viral genome

A

sitting within the lipid bilayer

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21
Q

describe the envelope on Sindbis virus

A

have both a capsid and lipid bilayer which contain protruding proteins

22
Q

spike proteins sit in the lipid bilayer, what does this induce

A

the immune response = antibodies

23
Q

describe the envelope of SARS-CoV2?

A

does not have a capsid, just a lipid envelope

24
Q

what surface proteins does SARS-CoV2 have?

A

spike glycoprotein, E protein and M protein

25
Q

which surface protein Is the target of the vaccine

A

spike glycoprotein

26
Q

what 2 proteins are embedded in the influenza envelope

A

neuraminidase

haemagluttinin

27
Q

what is the function of neuraminidase

A

used in viral exit

28
Q

what is the function of haemagglutinin

A

used in viral entry

29
Q

briefly describe how the astra Zeneca vaccine works

A
  • takes a chimp adenovirus vector and modified it to express SARS-CoV2 spike glycoprotein gene
  • recombinant virus is manufactured into gene
  • chimp virus is harmless to humans
30
Q

how many kilo bases in the SARS-CoV2 genome, is this large?

A

30

this is very large

31
Q

what is a polyprotein

A

large protein that is translated and cleaved into fragments - each fragment having its own function

32
Q

describe SARS-CoV2 genome

A

30 kb
no polyprotien
each protein is transcribed separately

33
Q

spike proteins bind to specifici plasma membrane receptors:

what does HIV bind to?

A

CD4 receptor on T-lymphocytes

34
Q

spike proteins bind to specifici plasma membrane receptors:

what does infleunza bind to?

A

sialic acid on glycoproteins

35
Q

spike proteins bind to specifici plasma membrane receptors:

what does rabies bind to?

A

acetylcholine receptor on nerve cells

36
Q

spike proteins bind to specifici plasma membrane receptors:

what does SARS-CoV2 bind to?

A

angiotensin converting enzyme 2 found on pneumocytes

ACE2

37
Q

how does Ebola virus enter cells?

A

using cholesterol transport protein

38
Q

how are individuals with Niemann-pick disease resistant to ebola

A

lack cholesterol transport protein

  • those who are homozygous = short life span & many symptoms
  • those who are heterozygous = less harsh symptoms & EBOLA RESISTANCE
39
Q

how do enveloped capsid viruses such as herpes simplex virus enter cells

A

receptors bind and the membrane fuses. here the contents are released into the cell and the capsid will dissolve and the viral genome will be released

40
Q

how do bacteriophages release the genome into the cell

A

bind via the tail pin and inject the core into the cell - releasing the genome

41
Q

how does HIV enter cells

A

binding to the variable region recruits a GPCR that conformationally changes, pulling the virus closer to the cell membrane

this results in a hydrophobic channel forming that allows the lipid bilayer to flow down the channel and the genome enters the cell

42
Q

how do viruses leave the cell

A

virus produces many copies which are encapsulated in a. vesicle

vesicle fuses with the membrane creating its own lipid bilayer before leaving the cell, stealing part of the host cell lipid bilayer.

43
Q

what does the capsid act to protect the virus from

A

harmful environmental factors such as UV

44
Q

give an example of a icosahedral virus

A

adenovirus

45
Q

what is the capsid made of

A

subunits called capsomers

46
Q

what are the two main capsid shapes

A

helical

icosahedral

47
Q

where is the viral envelope originally from, what do the viruses add to this

A

previous hosts (lipid bilayer from the host envelopes the virus as it leaves the cell via endocytosis)

viruses encode there own viral glycoprotein genes (e.g. spike proteins)

48
Q

which type of envelope is more susceptible to harsh environments

A

the lipid envelope

49
Q

what enzyme helps phages to enter the cell

A

lysozyme = weakens the cell wall at the point of attachment

50
Q

describe the replication cycle of a virus from the point the genome is inside the cell

A
  1. host DNA compartmentalised in a nucleus
  2. viruses with ssRNA form ds intermediate which can be used for mRNA synthesis
  3. transcription and translation occurs using host machinery
  4. assembly of new virus particles in the nucleus
  5. host plasma membrane is taken by new virus = pinches off by budding
51
Q

where does replication and assembly occur for poxvirus

A

in the cytoplasm

52
Q

what occurs in the eclipse period

A

cell contains viral components - but no complete particles

243: Medical Microbiology (27 decks)

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